1. A. Gupta, R. Liang, J. Moacanin, R. Goldbeck and D. Kliger, Macromoleculeds, 13, 262 (1980). PA0 2. D. Billies, P. Hrdlovic, and F. Manasek, Polym. Latt., 4, 1, (1966). PA0 3. A. Gupta, A. Rembaum and J. Moacanin, Macromolecules, 11, 1285 (1978). PA0 4. A. Factor and M. L. Chu, Polym. Degradation and Stability, 2, 203, (1980). PA0 5. D. T. Clark and H. S. Munro, Polymer Degradation and Stability, 4, 441, (1982).